The present invention is related to a cylinder type screen printing machine, and more particularly, to a paper discharging apparatus for transferring a printed paper.
However, the conventional discharging apparatuses have the following shortcomings.
Relatively thin paper tend to stick to the screen. Since papers are transferred along the screen in the first conventional discharging apparatus, it is difficult to separate paper from the screen. Further, printing is interrupted when a paper sticks to the screen.
The second conventional discharging apparatus transfers relatively thick paper along the printing cylinder. However, thick paper is relatively rigidity. Thus, when paper is separated from the printing cylinder, the end of the paper located on the opposite side of the end held by the discharging gripper may damage a screen during printing.
It is an object of the present invention to provide a paper discharging apparatus of a printing machine that is capable of discharging papers of various thickness.
To achieve the above object, the present invention provides a paper discharging apparatus of a screen printing machine. The screen printing machine includes a rotatable printing cylinder for guiding a printed sheet of paper to one of a first discharging position and a second discharging position. The paper discharging apparatus includes a first gripper unit for receiving the sheet at a predetermined holding position and transferring the sheet to the first discharging position. A first holding portion is defined in the first gripper unit to hold the sheet. A second gripper unit receives the sheet at the holding position and transfers the sheet to the second discharging position. The second gripper unit is adjacent to the first gripper unit at the holding position. A second holding portion is defined in the second gripper unit to hold the sheet. The position of the second holding portion is selectively shifted between a first position and a second position relative to the second gripper unit. The second holding portion is allowed to hold the sheet when the second holding portion is in the first position. The first holding portion is allowed to hold the sheet when the second holding portion is in the second position.
A further aspect of the present invention is a paper discharging apparatus provided in a screen printing machine to receiving a sheet transferred from an upstream location and transfer the sheet to one of a first tray and a second tray in accordance with the thickness of the sheet. The screen printing machine includes a printing cylinder reciprocally rotated between a print start position and a print end position. The paper discharging apparatus includes a first gripper unit fixed in a groove extending axially along a cylindrical surface of the printing cylinder. The first gripper unit receives the sheet when the printing cylinder is arranged at the print start position and releases the sheet when the printing cylinder is arranged at the print end position and the first gripper is adjacent to the first tray. A first holding portion is defined in the first gripper unit for holding the sheet. A second gripper unit moves in synchronism with the printing cylinder. The second gripper unit is arranged in the groove adjacent to the first gripper unit when the printing cylinder is in the print start position and arranged adjacent to the second tray to release the sheet when the printing cylinder is in the print end position. A stopper is provided in the second gripper unit and has a positioning surface. The positioning surface contacts a front end of the sheet to position the sheet. A second holding portion is defined in the second gripper unit to hold the sheet. The second holding portion includes a base selectively shifted between a first position and a second position relative to the second gripper unit. A gripper holds the sheet with the base. The positioning surface is downstream of the base and the gripper and the base hold the sheet when the base is in the first position. The positioning surface is upstream of the base and the first holding portion holds the sheet when the second holding portion is in the second position.
Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention